Gas turbine engines are used to power aircraft, watercraft, power generators, and the like. Gas turbine engines typically include a compressor, a combustor, and a turbine. A fan or propeller may be used to draw air into the engine. The compressor compresses the air and delivers higher-pressure air to the combustor. In the combustor, fuel is mixed with the higher-pressure air and is ignited. Products of the combustion reaction in the combustor are directed into the turbine where work is extracted to drive the compressor and, sometimes, an output shaft. Left-over products of the combustion are exhausted out of the turbine and may provide thrust in some applications.
In multi-shaft turbine engines, some of the engine components may drive or be driven by different shafts. Power can be extracted from these shafts to drive, for example, an electrical system. Some gas turbine engines may include a single gearbox mounted starter/generator or PMA (permanent magnet alternator), which may be used to provide power to the electrical systems.
The components of the engine and the electrical system have operational constraints or limits, beyond which component degradation or failure may occur.